Rotor blade and rotor blade assembly



April l, 1958 A. l.. MCCULLOUGH ET AL RoToR BLADE AND RoToR BLADE ASSEMBLY Filed Aug. 1

f mveNToRg ATTO RQ( SYS United States Patent 2,828,942 RoroR BLADE AND RoToR BLADE ASSEMBLY Application August 1, 1955, Serial No. 525,643

10 Claims. (Cl. 253-77) This invention relatesvto the assembly of blading in rotary power conversion machines such as compressors and turbines, and particularly to devices for preventing movement of the blades in one direction when they are already arranged forinter-locking relationship with the blade-supporting member in another direction.

'For instance, the invention relates to devices of this kind that will prevent movement of rotor blades in the axial direction in relation to the rotor, in a structure in which the root member of the blade enters a radially and axially extending bla-de slot in the rotor rim and the slot has an under-cut engaging the root section to restrain the blade from moving radially. An example of such mounting is the well known fir tree root arrangement.

One object of the invention is to provide an improved locking arrangement which will allow installation of the blades without the peening or hammering that is required to install some prior art locking arrangements. Another object is to provide a locking device which permits convenient removal of the blades and their replacement with the same locking device, thus providing for considerable re-usability of the locking device.

According to the invention, a blade stop is provided at one end of the blade root to engage the nearer face of the rotor and thus prevent relative sliding movement in one axial sense, and the blade is prevented from moving relatively in the other axial sense by means of a clip having a shank of resilient material that fits into the blade slot and has a stop at each end: a stop at the end near the blade stop for engaging the root member of the blade and a stop at they other end for engaging t-he rotor. The clearance between the blade root and the rotor slot is such that the resilient shank ofthe clip may be sprung so that one of the stops is held in a retracted position, out of engagement with the root portion of the blade or the rotor, as the case may be, while the blade is being inserted. When released the resilient shank springs back to bring the stop into operation.

In the drawings-in which each reference character indicates the same part in all the views- Fig'. 1 is a side elevation of a typical gas turbine engine. It is partly broken away to show in elevation a rotor blade attached to a rotor disc according to the invention.

Fig. 2 is a partly broken away perspective view of a rotor disc segment showing in spaced relationship a blade, locking clip and rotor assembly according to one form of the invention. l

Fig. 3 is a fragmentary sectional view taken on the line 3-3 in Fig. 2.

Figs. 4, 5 and 6 are views like Fig. 3 showing modified forms of the invention; and

Fig. 7 is a partly broken away sectionalview taken in a plane parallel to the rotor and through the flange of the rotor disc, showing the modied form of the clip that is illustrated in Fig. 6.

Each rotor blade 10 is secured in an under-cut blade slot 11 formed in the ange 12 of the rotor disc 13, which Wice exempliles any such blade-supporting member. The root member 14 of each blade has a blade stop 15-a flange designed to overlie one rface of the rotor llange. A central notch 16 divides the flange into two similar parts. This blade stop is preferably at whichever end of the blade root first receives the thrust on the blade in operation, so that it will restrain lthe blade against the sliding movement in the Islot 11 that would otherwise be caused by the thrust force.

The bottom part of the slot 11 has an area of greater depth defining a central channel 17 to accommodate a locking clip 19. The locking clip has a resilient shank 19B, and may be formed of a flat piece of resilient metal. It has a right-angle bend providing a projection or stop 20 extending away from the axis of the shank, and this stop has a 'further bend providing a handle 21 projecting generally in the direction of the shank so that this end of the locking clip can be easily moved by a finger or hand. The otherend of the shank 19a has a right-angle bend producing a second projection or stop 22 extending away rfrom the axis of the shank in a sense opposite to that in which the irst stop 20 extends.

The stops 20 and 22 are arranged so that when the locking clip is installed in the channel 17, one of the stops engages the root member by overlying a part of the end of the root that the blade stop is on, while lehe other stop engages the rotor. One of the stops is retractable. In the preferred form of the invention, the stop 20, which has the lug 21, is the retractable stop and it extends radially outwardly with respect to the rotor and overlies the end of the root 14 directly above (radially outwardly of) the central notch 16 in the blade stop 15.

To allow the retractable stop to be retracted, to permit for insertion and removal of the blades, the bottom surface of each of the root members is spaced from the bottom surface of the corresponding slot at the end of the slot near the retractable stop (lfor at least part of the length of the slot) to provide a radial clearance space 18. Ihis space allows room for springing the shank 19a of the locking clip in the sense opposite to that in which the retractable stop extends away from the shank, to retract it out of its locking engagement. In the preferred form of the invention, the bottom of the end of the channel near the blade stop 15 is sloped away from the circumference of the rotor to provide the clearance space 18 between the blade root and the rotor.

The clearance space should be at least as great as the -distance that the nearer stop extends away from the axis of the shank 19a, so as to allow the stop to be retracted fully out of its engagement with the blade root or the rotor, as the case may be. For example, in the preferred Iform of the invention, the space should be suflicient to allow the radially outer end of the stop 20 to be retracted at least to the general level of the bottom of the slot 11 to allow the root member 14 of the blade to be inserted in the slot.

The notch 16 in the blade stop 15 is designed to allow the blade stop 15 to pass over the stop 20 when the end of the locking clip 19 is retracted.

To install the blade the clip 19 is placed in the channel 17 with the stop 22 overlying the face of the rotor that is remote from the part of the channel that has been increased in depth.

The stop 20 is retracted into the clearance space in the channel and the blade is slid into the slot from the same end until the blade stop 15 engages the face of the rotor ange. When released, the stop 20 will overlie a part of the same end of the root member that the blade stop 15 is on, thus preventing movement of the blade toward that end.

In the modified form of the invention shown in Fig. 4,

Vthe channel 171 is made ofthe same radial depth from end to end as the maximum depth yot the channel 17 in Fig. 3, so that the clearance space extends for the full length of each slot, and the resilient shank 19.a1 of the clip is Apermanently bent to `provide Va supporting stop or lprojection 23 between the vends of the shank and extending away from the axis of the shank in Jthe same sense as the -stop 221. Thus the projection holds lthe lshank 19a against `the underside of the blade root, which is the side of the clearance space at which `the 'stop 201 operatively engages the structure. The resiliency ofthe shank enables rthe stop 201 -to be retracted as before. The stop '221 must be made suticiently long to engage therotor lin the `same way as stop 22 does in'Fig. 3.

Fig. S shows a modification in Awhich the stop on the end loi. Athe `shank remote from the blade stop, stop 222, lengages the rotor 'by being Areceived in a crosswise slot in the bottom of the channel 172 (instead of engaging one face of the rotor vas in Figs. 3, 4 and 6).

AIn Figs. 6 and 7 is -shown a refinement of the invention, designed `to prevent the clip 19a from being accidentally pushed out of the Vslot when the blade is `inserted by providing a lug 24 at the further bend (at the handle 21) and extending in the sense opposite to the sense in which the adjacent stop 203 extends. The lug 24 is punched out of the clip 193 at the bend for the stop 203 and bent down to engage the face ofthe rotor when the clip is retracted away from the blade root. In this position the clip 193 can be released while the blade is being 'pushed horne, without danger of the clip sliding with it.

What we claim as our invention is:

l. In a rotary power conversion machine, locking means for preventing movement of blading in a generally axial direction on a rotor having a number of generally axial slots in its circumference, comprising `blades having roots that interlock with the slots to prevent movement of the blades in any other direction, a blade stop on one end of each blade root `and engaging the rotor to prevent movement of the lblade root in one sense of the said axial direction, a locking clip ihaving a 4resilient shank lying between the rotor and each of the roots in each slot, each clip having a stop extending away from the axis of `the shank at each end of the shank, one of the stops engaging the root by overlying a part of the end of the root that the blade stop is on, the other stop engaging the rotor and one of the Istops being a retractable stop, the bottom surface of each of the roots being spaced from the bottom surface of the corresponding -slot Vfor at least -a part of the -length of Ithe slot at `the `end of the slot near the retractable stop to provide a clearance space, the dimension ofthe said space in the direction in which the retractable stop extends being at least as great as the distance that the retractable stop extends away from the axis of the shank to allow the shank to be displaced sutliciently to retract the stop out of its engagement with the root.

2. Locking means as claimed in claim l in which the clip is a strip of resilient metal having the said stops formed by a right angle bend at each end of the shank.

3. Locking means as claimed in claim 2 in which the retractable stop has a further bend providing a handle projecting generally `in the direction of the axis of the shank.

4. Locking means as claimed in claim 2 in which each slot has a channel receiving one of the clips, the bottom of the end'y of the channel near the retractable stop being sloped away Afrom the circumference of the rotor to provide the said clearance space.

5. Locking means as claimed in claim 2 in which the said space extends -for the` full length of each slot, and the clip 'has a supporting projection extending away from the axis of the shank in the sense opposite to the sense in which the said retractable stop extends away from the axis of the shank between the ends of the shank to hold the shank of the clip against the side of the space at which the said retractable stop engages the root.

6. Locking means as claimed in claim 4 in which the said space extends for the full length of each slot, the stops extend radially away from the axis of the clip, and the clip has a supporting projection between the ends of the shank to hold the shank of the clip against the blade root `in the channel.

7. Locking means as claimed in claim 1 in which the other stop overlies a part Aof the adjacent face of the rotor.

8. Locking means .as claimed in claim 1 in which the said other stop overlies a part of the face of the rotor that is remote lfrom the said end of the root member that the blade stop is on.

9. Locking `means as claimed in claim l in which each of the slots has a crosswise slot and the said other stop extends into the crosswise slot.

10. Locking means as claimed in claim 3 in which the clip includesva lug extending from the said retractible stop, in a sense opposite to the sense in which the retractible stop extends, to engage, when the said retractible stop is retracted, the face ofthe rotor.

FOREIGN PATENTS France Nov. 1, 1950 

